| Is it engine oil or clutch fluid?
The slave cylinder is a known soruce of leakage..........throw in a little muck and chain lube and it'll look like engine oil...........
When you refitted the pushrod, did you grease the o-rings up? They run in a fairly rough hole through the left hand casing. Fit them dry and they can tear.....
I'd guess it's the clutch slave cylinder though. | 
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